Short-circuiting device for electric motors



Sept 20 1927' F. J, BULLIVANT SHORT CIRCUITING DEVICE FOR ELECTRIC MOTORS Filed Feb. 18. 1924 .QN m\ mi f Il ulun. \\M v ,n 9, w m u um ////f Wm? J\ IMLI/l IIVW/ llllUA l NNW mw H .Qn @v m. Q Q x. m. I v2-3-1! il- I i Y mill) 5 nHHHHHHIUHHWHHJ.- .W w.

Patented Sept. 20, 1927.

UNITED STATES retain PATEr raies.

FRANCIS J'. BULLIVANT, OF ST. LOUIS, MISSOURI, ASSIGNOR TO VALLEY ELECTRIC COMPANY, OF ST.l LOUIS, MISSOURI, A CORPORATION F DELAI/VARIE.

SHORTCIRCUITING DEVICE FOR ELECTRIC MOTORS.

Application led February 18, 1924. Serial No. 693,519.

This invention relates to electric motors, and more particularly to mechanism for short circuitlng the rot-or winding', such as is used more particularly in motors of the single` phase type.

@ne of the objects of this invention is to improve the construction of such a short circuiting device so as to facilitate the operationthereof and render a lighter construction possible. 1

Another object is to provide an iu'iproved construction'for such a device which will be compactso as'to occupy small space.

Another object to provide en improved construction which will be cheap to manufacture and reliable in operation.

i Further objects will appear from the detail description taken in connection with the accompanying drawing, in which:

Figure l is a side view, partly in sect-ion. of a motor embodying this invention;

Figure 2 is a front end view of the centrifugal elements, and

Figure 3 is a perspective view of the mechanism. i

Referring tothe accompanying drawing, l designates the stator of usual construction provided. with bearings 2 carrying the shaft,

of the armature or rotor i. Mounted on the front of the armature is a commutator hub 5 carrying a commutator 6 constructed of a plurality of insulated segments in the usual manner and connected to the rotor Winding 7 of any desired type. In the present instance the colnmutator 5 is of the so-called radial type in which the brushes 8 bear yieldingly upon a radial face 9 of the commutator segments. The parts so far enumerated may he of any usual well known construction and will, therefore, require no further description.

The commutator 6 is provided with an internal bore 10 exposing the edges of the commutator segments. This bore 10 is of uniform dia-meter with the bore 11'of the commutator hub 5. Mounted for sliding movement on the shaft 3 and wit-hinthe bore 10-11 is a support or carrier 12. This support is adapted to fit loosely within the bore .10-11 so as to leave ample clearance therearound. The carrier 12 is further provided with an external annular groove or recess 13 adapted to receive a series of contacting elements 14. The elements 14 may each be provided with one or more perforations 15 through which a wire or other flexible connecting element may be passed so as to secure the elements 14. together. The elements lil are ordinarily formed by punching from sheet metal, usually copper, and a considerable number ofthem are strungupon a wire or similar means passed through tne perforations 15 so as tolform a string or so-called necklace of contacting elements. This string is then laid about the support 12 and within the groove 13 before inserting the support in the bore 10-11. The support 12 may be provided with 16 to which are pivoted a pair of links or 'cnsion mcmbers 17 pivotcd at their otherends to a pair of centrifugal elements 18. 'lf he elements 1S are of special form so as to surround the shaft 3 and are pivotedthereto at 19. The pivot 19 is placed on the shaft somewhat forwardly of the comn'iutator 6 and on the elements 18 forwardly of their center ofgravity Vso that when these elements move under the influence of centrifugal force, the bodies thereof will swing forwardly about the pivot 19. Surrounding the shaft 3 and between the centrifugal elements 18 and the hub of the support `12 is a coiled spring 2O bearing at one end against the hub of the support 12'and at the other against a washer or collar 21 surrounding the shaft 3 and restrained from movement thereon by a pin 22. The spring 2O thus provides a yielding abutment against which the support 12 hears.

Vrlhe spring 20 also urges said support rearwardly when the rotor is at rest. Rearward movement of the support 12 will spring the centrifugal elements 18 rearwardly and together against or close tothe shaft 8, and at the same time will carry the contacting elements 14C rearwardly so as to be out. of contact with the segments of the commutator 6. rPhe operation of this device is as follows: When the rotor is at rest, the spring 2O urges the support 12 to the rear carrying the elements 14- out of contact with the commutator segments and collapsing the centrifugal elements 18. lWhen the motor starts up and gathers a speed, a point will be reached where the centrifugal force acting on the elements 18 and tending to move it outwardly and forwardly will be sufficient to draw the support 12 forwardly by means of tension members 17 kwith sufficient force to overcome the pressure of the spring 20. The strength of the spring 2O may be adjusted so that this as indicated by the dotted line ,position` shown in Figure l. When in this po the elements 'ifi are adapted to form a series of bridges Connecting the individual.commutator segments with the hub 5 so as to short eireuit the eoinmutator. rihe rapid rotation of the rotor tends to throw the elements le outwardly with eonsi Yrable foi-ee so that a firm Contact is made both with the coininutator segments and with the hub There is thus provided an effective .short oirouit for the oonimutator.

It will, therefore, be seen that this invention accomplishes its objet A strueture is provided in which the cent iugai elements being` pivoted forwardly of their Centers of gravity viii upon moroni-at under the influence of oentrifiL force swing; forwardly. This structure further provides that these centrifugal may be mounted at the forvfard end of the'rotor which arrangement is adapted to improve the eompaetness of the neehanism and to save space, since the centi A`ig'al elements mounted adjacent the rest of the short oir- @uiting` mechanism and the connections therebetween are short so that space otherwise wasted may be utilized. L

11 further saving of space is attained at the rear end of the rotor at which point the centrifugal elements have heretofore beenl placed. l

In accordance with the present invention no moving mechanism is mounted at the rear of Vthe rotor so that the space occupied thereby is thus saved. The direct connection, between `the centrifugal elements and the other moving parts aise tends to reduce frietional resistance and thus render the operation of the device more reliable while at the same time making it possible to vreduce the size and cost of the various elements and thus Cheaper. the manufacture.

It is obvious that various changes may be made in details of construction Without departing from the spirit of this invention; itis, therefore, to be understood that this invention is not to be limited to the specific details shown and described.

Having- Vthus described the invention, what is claimed is:

. prisin l. In an alternating current motor having; a commutator at the front end thereof, means for short circuiting the eommutator oomprising, a `series of short-eireuii'iinrg elements adapted for movement forwardly to oon tact with the eommutator, a support for said Contact eleniients, and eentrifugai elements pivoted forwardly of the eommutator and connected to move said support forwardiy to contacting position.

2. In an alternating` current motor having a oommutator at the front end thereof, means for short eireuiting` the connnutator ooma series of short-Circuiti1 elements adapted for movement forwardly to e ntaet with the eommutator, a support for said Conelements, and centrifugal elements pivoted forwardly of said support and Connected to move said support forwardly to oontaeting position. K

8. In an alternating current motor havinga eommutator at the front end thereof, means for short eireuiting the eommutator comprising, a series of short-eireuiting elements adapted for movement forwardly to Contact with the commutator, a support for said contact elements, Centrifugal elements pivoted forwardly of the oommutator, and tension members Connected to said Centrifugal elements and adapted to move said support.

l. In an alternating current motor having eomniutator at the front end thereof., means for short cireuiting the eommutator eomprisinfr, a series of short-cireuiting elements adapted for movement forwardly to Contact with the commutator, a sliding supporIrl for said Contact elements, centrifugal elements pivoted forwardly of said support on said shaft, and links connected with said eentrifugal elements and adapted to slide saidY support forwardly to contacting position.

5. In an alternating current motor having;` a eommutator at the front end thereof, means for short circuiting the eommutator comprising, a series of short-circuiting elements adapted for movement forwardly to Contact with the commutator, a sliding support for said Contact elements, Centrifugal elements pivoted forwardly of said support on said shaft, links connecting said centrifugal elements with said support, and a yielding abutment between said. support and said. eentrifugal elements.

In testimony whereof I affix my signature this 22nd day of January, 1924-.

FRANCIS J. BULLIVANT. 

